CdS nanoparticles are incorporated into a poly(acrylic acid) (PAA) film associated with an An electrode, and the nanoparticles are covalently linked to the matrix. Cu2+ ions are incorporated into the CdS-nanoparticle-PAA film, and the electroswitchable photocurrent generation by the system, in the presence of triethanolamine as sacrificial electron donor, is demonstrated. The electrochemical reduction of the CdS-Cu2+-PAA state to the CdS-Cu-0-PAA state (-0.55 V vs SCE) leads to the formation of conductive metal nanoclusters that facilitate electron transfer of the CdS-conduction-band electrons to the electrode, and the generation of the photocurrent. The oxidation of the Cu-0 clusters to Cu2+ ions linked to the carboxylate units of PAA (applied potential +0.55 V vs SCE) switches off the photocurrent. The system not only is active for the reversible electroswitchable photocurrent generation but also acts as a photoelectrochemical detector of Cu2+ ions.